is a reservoir in some of the lower animals for leishmania, e.g. the house-lizard. The history of the Assam epidemic is against this view, for it has been definitely shown that the disease was introduced and spread by man, and that it did not pre-exist in the invaded districts, as would have been the case had there been an animal reservoir.
Predisposing causes.—— Kala-azar attacks both sexes and all ages, but, unlike malaria, it shows a predilection for the acclimatized the natives; in them it is said to be as severe and fatal as in the case of new-comers. In the Mediterranean basin it occurs almost though not quite exclusively in children (five months and upwards); in India it occurs at any age. The reason for this discrepancy as regards age has not been explained.
Incubation period.—— This is difficult to fix. In the case of one Englishman, recently under my care, the time that elapsed from his arrival in perfect health in the endemic region and the onset of the fever which terminated in kala-azar (diagnosed microscopically both before and after death) was under ten days. In a proportion of instances, as in some artificially infected dogs, and as is the case in dermal leishmaniasis, the disease may remain latent for months. In fatal cases in man the parasite may disappear from the tissues before death; what appears to be an explanation of this curious fact has lately been advanced by Archibald, who found certain coccoid bodies by hepatic puncture in these latent cases; he believes that these bodies represent a stage of the parasite.
Symptoms.—— Bentley, speaking from a large experience in Assam, and with full knowledge of the literature of epidemic kala-azar, says that the disease commences with high fever, which may be preceded by rigor and, in some cases, by vomiting. This initial fever—— intermittent in some instances, more frequently remittent—— may be very severe. It lasts for from two to six weeks, occasionally longer. During its progress the spleen and liver enlarge, increasing and decreasing at first, often in a most
